Linear-dimension gauge or comparator



Jan. 4, 1944.

J. LOXHAM LINEAR-DIMENSION GAUGE OR COMPARATOR Filed June 21, 1941 6shee'tssheet 1 11 Z10 X1 Z IN VLV'NTOR: JOHN LOXHAM BY ATTORNEYS v 1944-J. LOXHAM r 2,338,190

LINEAR-DIMENSION GAUGE OR COMPARATOR Filed June 21, 1941 6 Sheets-Sheet2 INVENTOB. J'OHIY LOX'HAM ATTOIRNEYYS I Jan. 4, 1944. JvLOXHAM LINEAR-DIMENSION GAUGE 0R COMPARATOR Filed June 21, 1941 e Sheets-Sheet s IINVENTOR.

JOHN LOXHAM Q1: zi g ATTORNEYS Jan. 4, 1944. LOXHAMLINEAR-DIMENSION-GAUGE 0R COMPARATOR Filed June 21, 1941 e Sheets-Sheet-4 INYENTOR:

J OH N LOX HAM .b E N R o T T A Jan. 4, 1944. LOXHAM 2,338,190

LINEAR-DI MEN SION GAUGE OR COMPARATOR Filed June 21, 1941 6Sheets-Sheet 5 Y INVEN RI JOHN LOXHAM V ATTORNEY;

Patented Jan. 4, 1944 LINEAR-DIMENSION GAUGE OR COMPARATOR John Loxham,Letchworth, England Application June 21 1941, Serial No. 399,064

In. Great Britain June 27, 1940 18 Claims.

This invention relates to linear-dimension gauges or comparators itschief object .being to evolve an improved linear-dimension gauge bymeans of which pieces to be measured may be readily compared with astandard measure, the results obtained being more highly accurate thanthose obtainable by similar instruments hitherto in use.

According to the invention the instrument comprises a measuring anvil orthe like adapted to move in a fixed straight path, the said measuringanvil being combined with means for translating its linear motion into arocking motion of a member-which is adapted to cause by its rockingmotion the actuation of means whereby ashaft or spindle carrying apointer is caused to rotate in such a manner that the radial angularmovement of the pointer is within very fine limits directly proportionalto the linear movement'of the measuring anvil. The said means for transalating the linear motion of the measuring anvil into a rocking motionmay comprise a movable frame or the like adapted to move under theaction of resilient means along a fixed straight path parallel with thefixed straight path along which the measuring anvil is adapted to move,movement of the said movable frame being nor- '.mally prevented bycontact between it and the measuring anvil or a member connectedtherewith but being permitted when the measuring anvil moves, themovable frame having associated therewith a flexible strip or likeelement whereto is connected a connecting member adaptedto be connectedalso to a second flexible strip which is associated with a second frameor the like, the said second frame being immcvable, and the arrangementbeing such that if the movable frame is ca'used to move along its fixedpath the said connecting member is caused to rock. The said connectingmember may have associated with it a pair of arms or like elements toeach of which is attached a flexible belt or other similardevice, thearrangement being such that if the connecting member is caused to rock,a motion of the said pair of arms ensues whereby a shaft or spindlecarrying a pointer is caused to rotate by means of the flexible belts sothat a radial angular movement is imparted to the said pointer. The saidpointer may be adapted to co-operate with a suitable scale so thataccurate measurements of the minute movements of the measuring anvil maybe made; or the said flexible strip associated with the movable frame,or the said connecting member, or the said shaft or spindle, may carry amirror adapted to receive a beam of light from a suitable source,

which beam, by means of a system including an additional mirror oradditional mirrors, is projected onto a screen or the like to provide areading; or the said pointer or a similar member may be, adapted tocarry a pen, whereby a record of measurement readings may be obtained ona movable chart. Preferably the piece to be measured is supported on anadjustable table arranged in a plane atright angles to'the path in whichthe said measuring anvil moves, means being.

provided whereby the said table can be made alternatively movable foradjustment or locked against movement. :Preferably, also, all or most ofthe indicating mechanism is enclosed in a box or casing, having afiushglass front arranged closely adjacent to the said scale wherewith thesaidpointer is adapted to co-operate.

The use .of two frames each carrying a flexible strip, the two flexiblestrips being joined by a connecting member adapted to rock and therebyto actuate a pointer, has previously'been the subject of a patent, No.1,392,239. The further features, hereinafter described, however, are

' novel, and in combination with the features Just mentioned they enablethe production of a precision instrument of remarkable sensitivenes'sand accuracy.

In order that the said invention may be clearly understood and readilycarried into effect, the to the accompanying drawings, in which: samewill now be further described with reference Figure 1 represents anelevation in perspective and partly in section of a linear-dimensiongauge exemplifying the invention;

Figure 2 represents in front elevation, partly insectlon, the baseiandcolumn;

Figure 3 is a side elevation of the base and column taken at the righthand side, viewing Figure 2; g

Figure 4 is a front elevation of the measuring and indicating device, aportion of the front plate bearing the scale being broken away to revealparts of the mechanism; 1

Figure 5 is a side elevation taken at the right handslde in relation toFigure 4; v

Figure 6 represents in front elevation a lid or cover adapted to besecured to the back plate to enclose the indicating'mechanlsm; and;

Figure '7 represents in elevation the inner side of the cover seen inFigure 6..

In this embodiment of'the invention, thespparatus comprises a base orstendA. to which which a nut E is adapted to co-operate, the ar-;.

rangement being such that on rotation of the nut E the table C will beelevated or lowered according to the direction in which said nut isrotated.

Rotation of the table C with its pillar D may be prevented by a key Fwhich is attached to .the pillar D, this key being arranged toslide intoa suitably cut slot in the base A when the table is raised or lowered.In order to eliminate back-' lash, the flanks of the'threads on the nutE and of those on the pillar'D are kept in close and constant contactand the lower face of the nut E is kept in close and constant contactwith'the base A by the force exerted by two springs, one, G, of which isshown, acting one upon each end ofthe'key F. When the table hasbeensuitably adiusted by means of the nut E, it may be clamped in acontrolled manner by means of a draw-bolt H- accommodated-in a suitableslot diametrically transversing the pillar D, which draw-bolt alsotraverses a part of the fixed base supporting balls as Q mounted in achannel shaped piece R, which is rigidly fixed to the back plate J andthe size of which is so arranged as to ensure that the balls Q are intrue rolling contact with the plunger L and the channel piece R, and asa consequence of this the plunger may.

be moved vertically up or down in a true straight line without play orfriction.

Mounted firmly on the back plate J is a frame S in the form, forexample, of an annular or preferably a horse-shoe shaped element whichis adapted to carry a flexible strip or torsion spring T, said flexiblestrip being tightly stretched across the frame diametrically thereof.Disposed adjacent to the first frame in such a manner as v to beslidable relatively thereto a second frame and is continually urged intolocking engagement with the pillar D by means of a suitably disposedspring h. The draw-bolt may be-manually withdrawn from'its operativeposition, the withdrawalbeing effected if desired through the medium ofan eccentric or other suitable means adapted to maintain thedraw-bolttemporarily in withdrawn position. r

Preferably the table C is made in the form of a flat plate as shown,attached to an enlarged portion a 'of the pillar D-by means of threesuitable screws as d. If the requirements ofthe work in hand are suchthat a'specially formed work-holder is desirable to support the work,the table C can be removed and "the specially shaped work -holdersubstituted therefor.

Adjustable arms, stops, or other fittings may,

I if desired, be mounted on the table'C to form a register for locatingthe part to be measured,

so that it may be speedily and accurately measured through any dimensionas predetermined.

The indicating mechanls'm'is carried upon a back plate J or similarstructure integral with or connected to a-rearwardly projecting bracketK or'the like which is adapted to co-operate with the column B in such amanner as to support the said mechanism, and also, if; desired, to allowvertical adjustment of the mechanism with respect to said column 13,means being provided to lock th mechanism in anyselected position.

If desired, the arrangement may be such' that the column B is formedwith a coarse screw thread or helical groove b and is adapted onactuation of an adjusting ring or the like which co-operates with saidthread or groove to be movable vertically either upwardly or downwardly.

A measuring anvil L is situated at the lower end of a cylindricalplunger L to which is attached a cross-head M and a topvplate N.Attached to the cross-head M are two springs P f It will be seen that ifU which is preferably annular and which carries a diametrically disposedflexible strip or torsion spring V which latter is adapted, when theframes are parallel and in alignment, to be accurately parallel with andalined with the flexible strip T carried by the first frames. The twoflexible strips T and V are suitably interconnected at or adjacent totheir centres, by a connecting member t which comprises three smallplates bolted together.

Interposed between the two frames S and U are suitably disposed balls asW, adapted'to allow movementof the second frame U relatively to theflrst S in 'a straight line truly parallel with the path of motion ofthe plunger L, the motion of the frame U being free from slidingfriction. This is arranged in the example illustrated by three V-shapedgrooves as U cut in the inner face of' the ring U and perpendicular tothe'longitudinal centre line of the flexible strips T and V and parallelwith plunger L. Two similar grooves are cut in the inner face of theframe 8 and situated immediately opposite two of the grooves in theframe U. Opposite the third groove in the ring U a flat surface isprovided onthe frame S and is so disposed that when three sphericalballs as W are fitted tothe three grooves as U in the fram U theflexible strips V and T attached to the frames U and S are parallel toeach other; The frame U is constrained to move vertically upwards and iskept in close and constant contact with the three supporting balls bymeans of the force exerted by two springs X, each of which is tensionedbetween two, of four transverse rods X which lie parallel in eightgrooves suitably placed in the outer faces of the frames U and S. Asmall pin 111- pressed into a hole drilled in the inner periphery of theframe U comes into contact with the underside of the plate N carried bytheplunser L and restricts upward movement which the springs X can giveto the frame U.

a small amountof vertical upward movement is given to the measuringanvil L through the frictionless plunger L and the frame U to theflexible strip V. The flexible strips T centre by the connecting membert, one of the plates of which is situated between them. Fixed sodisposed as to exert a horizontal and a smaller vertical pulling efforton the plunger L. The

horizontal pulling efiort ensures that the plunger L is kept in closeand constant contact" with four described. Attached to the outer ends totheconnecting member t are a pair of arms Y which are preferably soarranged as to be divergent at an angle of about 30, while beingslightly" offset one from the other vertically to facilitate thefixingof metallic ribbons Y carried thereby to a shaft Z, as will now bemore fully of the arms Y, one to each, are the two flexible ribbons Y,

metallic the free ends of which are adapted to the amount'of verticalthis same movement will be transmitted be clamped around a freelyrotatable shaft Z or around a collar or pulley upon the same, in such amanner that on vertical angular movement of the arms Y, due to rockingof the connecting membert, ,due in turn to a twisting movement of theflexible strips T and V, a rotary motion is imparted to the shaft Z.Mounted on the shaft Z is a pointer or the like a which is adaptedtoco-operate with scales 2" arranged at the front of the mechanism. Thescales 2" may be carried by a scale plate .2 pierced by a slot 2 ofarcuate form, the plate 2 being supported on a central bearing co-axialwith-the shaft Z so that the scale plate a is arcuately adjustablearound the said shaft. The scales z may beso arranged that some or allof the graduation lines thereon are not radial, as for instance at parta of the scale, and that a radial pointer will cut at least one line atsome point whatever the position of the pointer on the scale. Byobservingthe pointrately adjusted and if necessary a final adjustmentmay be made by moving the scale soth'at the pointer indicates thecorrect reading.

The movement of the pointer is obtained in the following manner. Onupward movement of the plunger L due to insertion on the table C-underthe measuring anvil L of the piece to be measyured, the plate N at theupper end of the plunger L will be moved upwardly in a direction awayfrom the pin 11 in the second or movable frame U, which frame is thenallowed to move upwardly with respect to the first frame S under theaction of the coil springs X associated with both frames. Relativemovement of the frames produces a twisting or angular movement of theflexible strips V and T with a consequent rocking of the connectingmember t and a corresponding anguat which the pointer cuts a non-radiallineonemay obtain a more minute reading than is possible with a scale onwhich only radial lines are) employed. The arrangement may be such-thatthe moving pointer moves in-the same plane as} the scale; and by thismeans errors due to parallax are eliminated. In the exampleillu strated,this is eflected by bendingv outwardly the lar movement of the arms Y,which last movement results, as above explained, in a rotary motion oftheshaft-Z carrying the pointer z, the pointer being thus movedrelatively to the scales zto indicate the thickness of the piece beingmeasured. Y

After setting of theapparatus, by measurement of. a standard piece,pieces to b compared withthe 'standardmay then' be placed successivelyin position on the table. and the readings taken,

end of the pointer s so that it enters the slot 2'.

' If desired, the adjustment of the scale maybe effected by a rotatablerod 2 or the like which is, wholly or partially threaded and is adaptedto cooperate with a correspondingly threaded fixed element a", so that,on rotation, the rod 2 moves longitudinally, the end of the said rodbeing adapted to co-operate with a suitable abutment 2 carried by thescale plate' 2 while a spring 2 is provided to maintain the abutment etact with the rod .2 I

Means are provided for lifting the plunger L when so desired, such meanscomprising for'exthe previous setting of the instrument being,oi cgurse,retained. As each piece is inserted un- I der the measuring anvil l, theconsequent angular or twisting movement of the flexible strips TandcVwith the associated rocking of the connecting member tis proportional tothe vertical movement of the plunger L; and the movement of saidconnecting member is multipliedby means of the arms Y in sucha manner asto give an appreciable movement of the pointer z.

in conample a manually :operable lever F'which is mountedon a freelyrotatable shaft, which latter is adapted to carry an arm 1 or arms soarranged that on depression of the lever said .arm li will abut againsta stop 1 or stops carried by" the plunger L and will urge the same iupwardly. Preferably a spring 1 is associated with the arm 1 serving toreturn the same and the'lever l to,

their initial positions on releaseof pressure on the said lever, andhence to allow return of the netic damping eifqrt of the disc z", willbe'pro portional-to the speedofzrotation of the shaft Z, being atits'maximum when the pointer tends Preferably magnetic damping means areassociated with the shaft Z carrying the pointer z; so that on operationof the instrument the said pointer will assume its appropriate positionwith respect to the scale without undue oscillation.

For example, there is provided a permanent ma netic!" rigidly supportedwith its poles adjacent to a disc 2 of electrical conductingmaterialfixed upon. and rotating with the shaft-Z. The mat!- to turn mostviolently but beingnil when the pointerisat rest. I v

The back plate J whereon all the fixed-parts I plunger L under theaction of its springs? toits,

initial position.

Aremovable stop 1 working in contlunction with the lifting mechanism mayco-operate with another arm I" on the shaft which carries the arm 1 soas-to reduce the amount of lift'that canv be given to the plunger L.thus preventing shock being transmitted to the mechanism by reason ofthe plunger being allowed to fall through a large.

distance. When occasions arise where'ia large lift of the plunger L isnecessary, the stop 1 c be withdrawn, and in these circumstances spec alcare should be exercised in lowering the plunger. In operating theinstrument, a standard piece i placed in position on the table ,0 andthe measuring anvil L at thefilower end of the plunger L is broughtintocontact with the top surface of the piece, th apparatus beingadjusted until the correct reading is obtained with'the scales 2 andpointer 2. If necessary, an initial coarse adjustment may be made byadiustingthe position of the indicating mechanismrvertically withrespect to the column B. After such coarse adjustment, the table Citself may then be accuof: the indicating mechanism 'are mounted mayconveniently be adapted-to co-operate with a- '66 suitable cover so thatthesaid backplate and cover together form a box .or casing adapted toenclose all or most of the indicating mechanism,

provision being made owever for the measuring anvil L' to projecttherefrom. The said box or casing may have a front adapted to bepositioned parallel with the said backplats J and closely adlacent tothe scale-plate a the said front'being glazed to allowthe scale z to beseen'through it. This cover may conveniently-b constructed'asrepresented in Figures 6 and 7. Its front H is r partly cut away/toprovide a rectangular aperture adapted to accommodate a glass plate I!of the'same shape as the said aperture and of approximately the samesize. The edges of the said aperture and the edges of the glass plate I!are correspondingly bevelled in such amanner that the glass plate 12 isadapted to be pressed into the aperture with the bevelled edges of theglass plate I! coinciding with the bevelled edges oi the aperture. thearrangement being such that g the glass plate I! lies flush with thefront II, and thus flush with the forward edges of the four sides of thecover. In the cover illustrated, the glass plate I2 is pressed into theaperture from underneath or behind the front ii, and is held in positionby four finger-clips l3 screwed to the under side of the said front.

Preferably the front I i carries adjustable means for defining therequired limits of tolerance, positive or maximum and negative orminimum, in the use of the gauge. In the example shown, the saidadjustable means comprises two Wire finacre 14, i adapted to lie underthe glas plate ii in close juxtaposition thereto, in such a positionthat when thecover is in place over the mechanism they will appear tocross the slot 2 in the scale-plate 2 the said wire fingers 14, I5,being adapted to be, by manual operation, moved along the scale a withan angular motion approximately concentric with the angular motion ofthe pointer 2 This manual operation of the wire fingers l4, I5 iseffected by means of two knobs i6, i1 arranged to project from th frontIi, each of the said knobs being rigidly secured upon a small spindle orpin which passes through a suitablebearing hole in the front Ii and isassociated with friction gearing supported at the back or under side ofthe front Ii. This friction gearing shown in Figure 7, comprises twosmall discs I 8, I9 of thin sheet metal, rigidly secured upon therespective inner ends of the two spindles or pins upon the outer ends ofwhich the knobs l6, I! are secured. The discs I8, I! are arrangedrespectively to bear frictionally upon members 20, H which are likewiseof thin sheet metal and are of a shape approximating to a sector'of acircle, these sector members 20, 2! being to a certain extent revolvableabout a suitably formed axis member 22 which is attached to theunderside of the front II by screws 23. The

arrangementis such that by manual turning of V the knob IS the disc I!rotates and by its friction upon the sector member. 20 cause this sectormember to revolve to some extent around the axis member 22 so that thewire finger I4 is caused to move upwards or downwards as desired to makea higher or lower positive limit of tolerance. Similarly by motion ofthe knob IT with the disc i9 and the sector member-2i, the wire fingerI! is caused to move upwards or downwards to mark a higher or lowernegative limit of tolerance.

Instead of the above-described construction, an optical .indicatingsystem may be employed, in which case it is preferred that the arms Y,the flexible metallic ribbons Y, the shaft Z, and the pointer e, beeliminated, a mirror or the like being mounted centrally of the flexiblestrips T and V, as for instance being affixed flat upon one of theplates of the connecting member t. In such cases a suitable source oflight would be incorporated in the device and arranged to project a beamof light on to said mirror, which beams, by means of a suitable systemincluding one or more additional mirrors, would be promovable frame soto move, a stop disposed in the path of the said movable frame whichstop is connected with the said measuring anvil, a flexible stripconnected with the said movable frame, a second frame which isimmovable, a second flexible strip connected with the said second frame,a connecting member which connects the two said flexible strips togetherand is rockable by distortion of the said strips, a spindle, a pointercarried by the said spindle and rotatable therewith, means associatedwith the said connecting member by which means the spindle and pointerare caused to rotate, and a table adapted to support the piece to bemeasured, which table is disposed beneath the said measuring anvil, thearrangement beingsuch that normally the said stop holds the saidmovableframe immovable but if the said measuring anvil moves and thestop with it, the said movable frame is moved by the action of the saidresilient means, causing distortion of the two said flexible strips androcking of the connecting member to actuate the said means associatedtherewith whereby the pointer is caused to rotate, its angular movementbeing within very fine limits directly proportional to the linearmovement of the said measuring anvil.

2. A linear-dimension gauge according to claim 1, wherein the saidconnecting member has operatively connected with it a pair of arms toeach of which is attached a flexible belt whereby when the connectingmember is caused to rock, movement is thereby imparted to the said pairof arms jected on to a screen or the like to provide a reading.

What I claim and desire to secure by Letters Patent of the United Statesis:

i. A linear-dimension gauge comprising a measuring anvil, guiding meansto render said anvil movable only along a fixed straight path, a movableframe which is'movable along a fixed straight path parallel-with thefirst-named fixed straight path, resilient means urging the said wherebya rotary movement is transmitted to a shaft carrying a pointer, by meansof the flexible belts, and the pointer is thus caused to perform anangular movement.

3. A linear-dimension gauge according to claim 1, wherein the saidpointer is adapted to co-operate with a suitable scale so that accuratemeasurements of the minute movements of the measuring anvil may be made.

4. A linear-dimension gauge according to claim 1, wherein the saidmovable frame moves upon ball bearings whereof the balls areaccommodated in V-shaped grooves or like channels formed in the adjacentco-operating faces of the two frames, the saidgrooves being so arrangedthat the motion of the movable frame is maintained in a straight line.

5. A linear-dimension gauge according to claim 1, wherein the saidresilient means comprise coiled springs tensioned between the movableframe and the immovable frame, the arrangement being such that the saidsprings tend both to pull the movable frame towards the immovable frameand also to urge the movable frame to move in relation to the immovableframe.

6. A linear-dimension gauge according to claim 1, wherein the said shaftor spindle carrying the pointer carries also a disc or the like ofelectrical conducting material arranged within the field of a magnet, inorder that violent movement of the said disc and so of the said shaft orspindle may be magnetically damped or restrained.

7. A linear-dimension gauge according to claim 1, comprising aplunger towhich the said measuring anvil is attached, which plunger is movablelongitudinally, a channel arranged lengthwise of the plunger;anti-friction bearing balls suitably disposed in the said channel, andresilient means to constrain the plunger to lie upon the said balls.

8. A linear-dimension gauge according to claim 1, comprising a plungerto which the said measuring anvil is attached, which plunger is movablelongitudinally, a channel arranged lengthwise ofthe said spindle forthepurposeof adjusting the the said plunger, anti-friction bearing ballssuitably disposed in the said channel, and resilient means to constrainthe plunger to lie upon thesaid balls, and simultaneously to urge theplunger to move in the direction of the measuring anvil.

9. A linear-dimension gauge according to claim 1, comprising a plungerto which the said measuring anvil is attached, which plunger is movablelongitudinally, a channel arranged lengthwise of the said plunger,anti-friction bearing balls suitably disposed in the said channel,resilient means to constrain the plunger to lie upon the said balls, andstops wherewith the plunger is adapted to co-operate in such a mannerthat the extent of the movement permitted to the plunger is limited.

10. A linear-dimension gauge according to claim 1, comprising a plungerto which the said measuring anvil is attached, which plunger is movablelongitudinally, a channel arranged lengthwise of the sand plunger,anti-friction bearing balls suitably disposed in the'said channel,resilient means to constrain the plunger to-lie upon the said balls, andmanually operated means, operatively connected with the plunger, andadapted to move the plunger against the eilort f the resilient meansassociated therewith.

11. A linear-dimension gauge according to claim 1, comprising a plungerto which the said measuring anvil is attached, which plunger is movablelongitudinally, a channel arranged lengthwise of the said plunger,anti-friction hearing balls suitably disposed in the said channel,resilient means to constrain the plunger to lie upon the said balls,manually operated means, 0peratively connected with the plunger andadapted to move the plunger against the effort of the resilient meansassociated therewith, and a stop or stops adapted to limit the extent ofthe movement permitted to the plunger, with which stop or stops the saidmanually operated means is adapted to co-operate.

12. A linear-dimension gauge according to claim 1, comprising a pair ofarms associated with the said connecting member, and two flexible belts,each arm of the said pair having attached to its outer free end one endof one of the said belts, the other ends of the said belts being coiledaround the said spindle carrying the said pointer, the arrangement beingsuch that if the sa d arms are moved by reason of the rocking 0f thesaid connecting member, the said rocking is translated in a multiplieddegree into a rotary motion of the said spindle.

13. A linear-dimension gauge according to claim 1, comprising ascale-plate wherewith the said pointer is adapted to co-operate, inwhich scale. in accordance with the position of the pointer, and aspring adapted to maintain the said abutment in contact with the saidthreaded rod.

15. A linear-dimension gauge according to claim 1, comprising a tableadapted to support the piece to be measured, which table is arranged ina plane at right angles to the path in which the scale-plate is providedan arcuate slot upon the edge of which a suitable scale is marked, thesaid scale-plate lying in a plane adjacent to and parellel with theplane wherein the said pointer moves, and the end of the pointer beingbent to enter the said slot and to lie in the same plane as the scale,so that reading errors due to parallax may be eliminated.

14. A linear-dimension gauge according to claim 1, comprising ascale-plate wherewith the said pointer is adapted to co-operate, thesaid scale-plate being revolvable around the said spindle carrying thesaid pointer. an abutment associated with the said scale-plate, a fixedelement,

a threaded rod adapted to pass through the said fixed element and tobear upon the abutment so as to cause the said scale-plate to revolveabout said measuring anvil moves, an externally threaded pillarsupporting the said table, a fixed base means for providing a downwardpull upon the. pillar for the purpose of preventing backlash be! tweenthe threads of the pillar and those of the nut, said means comprising amember associated with the-pillar and springs disposed between a part ofthe fixed base and the said member, and means for locking the saidpillar against movement.

16. A linear-dimension gauge according to claim 1, comprisingatable'adapted to support the piece to be measured, which table isarranged in a plane at right angles to the path in which the saidmeasuring anvil moves, an externally threaded pillar supporting the saidtable, a fixed base wherewith the said externally threaded pillar isadapted to co-operate, a correspondingly internally threaded nut screwedupon the said externally threaded pillar and arranged between andparallel with the lower surface of the said table and the upper surfaceof the said fixed base, the arrangement being such that rotation of thesaid nut causes the said pillar and table to move towards or away fromthe said measuring anvil, means for providing a downward pull upon thepillar for the purpose of preventing backlash between the threads of thepillar and those of the nut, said means comprising a member associatedwith the pillar and springs disposed between a part of the fixed baseand the said member, and means for locking the said pillar againstmovement, which latter means comprises a drawbolt accommodated in asuitable slot diametrically traversing the pillar, the said drawboltalso traversing a part of the fixed base, a nut on the end of thedrawbolt, and a helical spring disposed around the drawbolt between thesaid nut on the end thereof, and the outer surface of the said part ofthe fixed base tending to urge the drawbolt continually into lockingengagement with the.

measuring anvil moves, an externally threaded pillar supporting the saidtable, a fixed base wherewith the said externally threaded pillar isadapted to co-operate, a correspondingly internally threaded nut screwedupon the said ex ternally threaded pillar and arranged between andparallel with the lower surface of the said table and the upper surfaceof the said fixed base. the arrangement being such that rotation of thesaid nut causes the said pillar and table to move towards or away fromthe said measuring anvil,

means for providinga downward pull upon the pillar for the purpose ofpreventing backlash between the threads of the pillar and those of thenut, said means comprising a member associated with the pillar andsprings disposed between a part of the fixed base and the said member,and means for locking the said pillar against movement, which'l'attermeans comprises a drawbolt accommodated in a suitableslct;diametri-cally traversing the pillar, the said drawbolt alsotraversing a part of the fixed base, a nut on the end of the drawbolt,and a helical spring disposed around the drawbolt between the said nuton the end thereof and the outer surface of the said part of the fixedbase tending to urge the drawbolt continually into lockingengagementwith the pillar, the arrangement being such that the drawbolt can beremoved from looking engagement 'with the pillar by a sufficient degreeof manual maintain the drawbolt temporarily in withdrawn position.

18. A linear-dimension gauge according to claim l,- comprising abackplate whereon all the fixed parts of its indicating mechanism aremounted, a suitable cover adapted to co-operate with the said backplateso that backplate and cover together form a box or casing adapted toenclose all or most of the indicatin mechanism, provision being madehowever for the measuring anvil to project therefrom. said box or casinghaving a glass front arranged parallel with the said backplate andclosely adjacent tothe scale-plate. the said glass front being arrangedflush with the forward edges of the four sides of the said cover, andbeing provided with adjustable means to define the required limits oftolerance in the use of the gauge.

JOHN LOXHAM.

